Detergents used for washing tableware (i.e., glassware, china, silverware, plastic, etc.), kitchenware, and household surfaces have long been known. The particular requirements of cleansing tableware and leaving it in a sanitary, essentially stainless, residue-free state has indeed resulted in so many particular compositions that the body of art pertaining thereto is now recognized as quite distinct from other cleansing product art. Likewise, the bodies of art pertaining to other household cleaning, such as fabrics, floors, hard surfaces, bathroom fixtures, are each immense and encompass many formulations designed for stain removal. Many formulations in each field include bleaches.
However, consumers continue to experience problems with stain removal on various substrates, including typical kitchenware surfaces and appliances. In particular, formulators have experienced difficulties in formulating detergents and cleaning compositions wherein the bleach is mild to the skin but has sufficient strength to perform adequately on tough stains and soils. Typically for stain removal, formulators have turned to chlorine bleach or sources of hydrogen peroxide and bleach activators.
Numerous substances have been disclosed in the art as effective bleach activators for laundry use. One widely-used bleach activator is tetraacetyl ethylene diamine (TAED). TAED provides effective hydrophilic cleaning especially on beverage stains, but has limited performance on hydrophobic stains, dingy stains and body soils. Another type of activator, such as nonanoyloxybenzenesulfonate (NOBS) and other activators which generally comprise long chain alkyl moieties, is hydrophobic in nature and provides excellent performance on dingy stains.
It would seem that a combination of bleach activators, such as TAED and NOBS, would perform well on both hydrophilic and hydrophobic soils and stains. However, many of the activators developed thus far have been found to have limited efficacy, especially at use temperatures below 60.degree. C., which is common for dishcare and household surface cleaning. Another consideration in the development of consumer products effective on both types of soils is the additional costs associated with the inclusion of two or more bleach activators. Accordingly, it is of substantial interest to the manufacturers of bleaching systems to find a less expensive type of bleaching activator.
Chlorine bleaches are effective for stain and/or soil removal. While chlorine bleach is a very effective cleaning agent, it is not compatible with a variety of detergent ingredients and may require lengthy soaking time in which the bleach and the stained substrate must remain in contact to ensure stain removal. Another known bleaching source is diacyl peroxides (DAPs). Although DAPs have been disclosed for use in the laundry and anti-acne area, they have had limited success in liquid detergent areas. In the laundry field certain diacyl peroxides have been disclosed as beneficial in cleaning tea stains from fibrous material. It has now been discovered that DAPs can improve stain removal performance on plastics.
Another problem facing formulators is stability of the bleaching agents and other individual ingredients over time, especially in liquid products. This is particularly true for diacyl peroxides in alkaline conditions. Bleaching agents have been encapsulated to provide stability. Yet encapsulation leads to problems such as reduced dosing because of incomplete dissolution of the encapsulating material and to delayed introduction of the bleaching agent into the wash liquor.
As a consequence to the above-identified problems, there has been a substantial amount of research to develop bleaching systems which are stable and effective in liquid formulations and which remove a wide variety of stains.
By the present invention, it has now been discovered that certain bleaching agents are stable and perform very well on stains when the bleaching agent is first activated by microwaves and then applied to the substrate to be treated. Accordingly, the present invention solves the long-standing need for an inexpensive bleaching system which performs efficiently and effectively under mixed soil load conditions and is effective for a variety of substrates.
The detergent compositions provided herein have the property of removing stains, especially tea, fruit juice and carotenoid stains objected to by the consumer from plastic dishware, glass, wood, ceramic, household surfaces, and many other known substrates when the composition is first exposed to microwaves from any typical household or commercial microwave appliance. The compositions have other cleaning benefits in addition to stain removal advantages such as deodorizing and disinfecting. Thus, provided herein is a method of removing stains from a substrate by applying an activated bleaching compositions which has been subjected to microwaves.